As is well known to those skilled in the art, aromatic hydrocarbons in middle distillate fuels such as gasoline or diesel oil represent a source of atmospheric pollution. The aromatic content of those middle distillates may be as high as 85 v %. An illustrative light straight run gas oil may for example be typically found to contain 30 v % aromatics. As environmental considerations become of greater concern, it is desirable to treat middle distillate hydrocarbons to decrease the content of undesirable aromatic components.
U.S. Pat. No. 3,997,473 (and its divisional U.S. Pat. No. 4,032,435) is directed to hydrodesulfurization of petroleum residues by use of a cobalt/nickel with molybdenum or tungsten on carbon catalyst which is characterized by an average pore radius of at least 25 .ANG. and a BET Surface area of 200-800 m.sup.2 /g. The catalyst of these patents has a loading of VI-B metal "of at least 10 and up to about 20 weight percent expressed as metal oxide based on the weight of the catalyst support."
U.S. Pat. No. 4,082,652 is directed to treatment of heavy oils, such as gas oils, to effect hydrodesulfurization by use of a molybdenum/nickel on carbon catalyst. The catalyst preparation requires that the molybdenum be deposited first then sulfided, and only then that the nickel be added.
U.S. Pat. No. 3,546,103 is directed to the removal of metals and coke from hydrocarbon resids by use of, as precatalyst, metals of Group II-B or VI-B plus VIII on charcoal.
U.S. Pat. No. 3,367,862 is directed to desulfurization of heavy residual hydrocarbons by hydrolysis with water in the presence of catalyst on a char base.
U.S. Pat. No. 3,812,028 is directed specifically to "hydrotreating" fossil fuels containing polynuclear aromatics such as asphaltenes for converting the components boiling above 1000.degree. F. to products boiling below 1000.degree. F. (this is actually hydrocracking), by the use of Group VI and/or Group VIII metals on carbon, at a hydrogen partial pressure in excess of 2200 psig and at temperatures between 750.degree. F. and 850.degree. F.
U.S. Pat. No. 4,313,852 is directed to hydrotreating, particularly of coal liquids, in the presence of carbon supported molybdenum or tungsten sulfide catalysts with or without a second metallic component, in which catalysts the metal sulfides are substantially completely exist on the outer surface of the active carbon support. The carbon supported catalyst preparation according to U.S. Pat. No. 4,313,852 must involve direct deposition of metal sulfides on the carbon support and subsequent reduction of them to lower valent sulfides.
U.S. Pat. No. 5,051,389 is directed to a method for preparing a catalyst composition for hydroconversion processes wherein the catalyst composition is formed by depositing one or more metal and/or metal compounds onto a preformed carbon support which has maximum dimension in any direction from about 50 Angstroms to about 500 Angstroms, from the vapor phase at elevated temperatures. The catalysts made according to U.S. Pat. No. 5,051,389 have to be added to or combined with the carbonaceous material to be hydrotreated in only 50 ppm to 5000 ppm concentration for the hydroconversion process to take place (one-pass application).
U.S. Pat. No. 3,725,303 is directed to treating of aqueous solutions of oxy-sulfur compounds (such as sodium thiosulfate) by use of a catalyst containing molybdenum sulfide and cobalt sulfide on carbon support.
It is an object of this invention to provide a novel process and catalyst for hydrodearomatizing middle distillate hydrocarbons. Other objects will be apparent to those skilled in the art.